The present invention relates to industrial vision systems, and more particularly to a sealed focusing assembly for an industrial vision system.
In the early 1960's industrial automation underwent a revolution with the advent of practical industrial robots. As technology has advanced, industrial robots have become more sophisticated. One area of technology that is currently undergoing remarkable change is the area of sensory means for industrial applications, particularly robots.
In order to function properly in the workplace, industrial robots must be able to detect the environment they operate within. Robotic sensing may be tactile in nature, such as where a robot physically contacts its work environment and responds to the contact forces. Alternatively, non-contact sensing may be employed. Such non-contact sensing means employ either proximity sensors, that are sensitive to the distances between objects, or vision sensors, such as cameras. Naturally, non-contact sensors are preferable in many situations, such as where a sensing system is employed for manufacturing that requires extremely accurate tolerances.
Industrial vision systems are based on the processing and interpreting of electrooptical images. Frequently, such systems are part of an industrial robot that may be programmed to carry out a large variety of tasks. Often such vision systems utilize multiple visions sensors, such as cameras, sending multiple sensory signals to a computer for sorting and processing.
A fundamental component of any industrial vision system is the focusing assembly which contains a lens or lens assembly, that is directed at the item that it is desired to view. The "objective" is the focusing assembly which contains the lens that is exposed to the environment, and which comes in first contact with the light from the item being viewed. The objective forms an image of the object at its focal point. If a lens assembly is employed, multiple lenses are arranged in order to rotate, or magnify the images produced by the lenses.
Depending on the particular lens orientation and assembly, the focal length of the focusing assembly will vary. Thus, if the distance between the item to be viewed and the focusing assembly of the vision system is changed, the vision system will have to be focused. Focusing may take place by adjusting the focusing assembly in order to change the distance between the lens assembly and the optical detector, the device that is sensitive to the light transmitted by the lens assembly. Such adjustment can take many forms, for example by cam motive means or by threaded motive means located between the lens assembly and the optical detector within the focusing assembly. Industrial vision systems, and more generally, focusing assemblies and their methods of operation are known in the art. For example, Forkey discloses a Fluid Sealed Lens Mounting System in U.S. Pat. No. 4,718,750, comprising a body assembly, a carrier and lens carried within the carrier, which is focused by cam operation.
Industrial vision systems are currently used in many industries for a variety of applications. For example, vision systems may be used in industrial manufacturing to inspect, identify and count parts. When combined with an automated robot assembly, industrial vision systems may be used to guide robots so they can sort, position, orient and test parts and assemblies.
In addition to manufacturing, industrial vision systems have been utilized during post-manufacturing, such as for quality control of finished parts. Vision systems may be used to check shape and size defects, the number and size of components, and to measure critical dimensions of finished components such as surface integrity, thus allowing the rejection of unsatisfactory components.
Many industries have utilized industrial vision systems in manufacturing and quality control. The automobile industry was the first to use automated robots generally. The industry has used robots that employ vision systems for a number of applications such as welding of sheet metal parts, and the manufacture of transmissions, engines, plastic body panels, dash boards and electrical systems.
Other industries such as the electronics and aviation industries have utilized industrial vision systems for manufacturing items such as printed circuit boards or keyboards, and bearings, motors and relays.
Industrial robots that employ vision systems have several benefits over their human predecessors. Vision systems may ensure high quality products as the systems are capable of being extremely accurate and are designed for repeatability, often at high speeds. The vision systems also allow automatic, accurate and safe handling and control of materials, whether the materials are hazardous or not. In addition, if the systems are small enough, they can be located in almost any position and, in environments that would otherwise be hostile to humans, such as at extremely high temperatures, often necessary for manufacturing.
However, certain inherent characteristics of industrial vision systems cause problems that the industry has attempted to resolve. For example, many of the current industrial vision systems work in operating environments where they may encounter dirt, gas fumes, fluids, dust, chips, weld splatter, etc. Due to the need to axially shift a lens assembly within the focusing assembly in order to focus the vision system it is necessary to have separate housings for the lens assembly and the optical detector so they can be moved with respect to one another. Thus, the location where the housings connect is a potential entry way for debris from the work environment, which may damage or otherwise interfere with their proper operation.
Additionally, changes in the temperature and humidity of the work environment may cause condensation on the lens assembly. Of course, such potential debris and condensation on the lens assembly may render a vision system inaccurate, and therefore, useless. These problems have created the need for systems that are sealed from the work environment. Typically, vision systems used in industrial applications in which sealing of the lens/housing assembly is a requirement use the following methods to seal: an unsealed camera may be placed in a sealed enclosure with a window; other, more sophisticated units, use specially sealed lenses which are capable of only splash resistant sealing; still others, use unwieldy and complicated assemblies and sub-assemblies that require the detector be positioned to allow focusing, such as that disclosed in the Forkey patent, mentioned previously, and Quammen et al, U.S. Pat. No. 3,246,563, where a bellows type seal is employed.
Another problem encountered occurs when extremely high accuracy, i.e. tight tolerances, are necessary. The structure of most lens assemblies is such that when the lens is focused, generally by rotation of an adjustment ring, the lens itself is concurrently rotated. Therefore, concentricity tolerances between the lens and the housing assemblies must be extremely accurate to prevent target misalignment during focusing. Quammen et al, U.S. Pat. No. 3,246,563 discloses a telescopic eyepiece assembly in which the lens moves only axially upon rotation of the adjusting ring. However, this is accomplished in the context of a complex, bellows-type arrangement that is large and unsatisfactory.